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Explanation of the difference between SCS WDS


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39 minutes ago, humeur said:

Hello;

I can't understand the difference between these two terms, the advantage or disadvantage of using one better than the other.

 

 

JL
 

I guess it depends on the software, some were written only for wds from the Myarc hdfc days.

 

I think scs was added do you could have both a Myarc hdfc and SCSI card in the same peb, I have both but haven't try that yet, as I don't have any mfm hard drives or emulator device.

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WDSx is from the HFDC ROM (Winchester Drive System, I would read it) and originally meant a MFM hard drive (like the Seagate ST251).

HDSx is from GeneveOS (Hard Drive System). It is used to access the hard disks on the HFDC card, but uses the Master DSR from GeneveOS.

SCSx is from WHTech SCSI or ASCSI.

 

However, the SCSI card ROM also defines WDSx, so I guess this is for the sake of compatibility (if software assumed that a HFDC is present).

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29 minutes ago, Gary from OPA said:

Also should be noted that originally only wds1, wds2, wds3 existed for Myarc hdfc.

 

Whereas SCSI allows up to 7 devices.

Peripheral Device names
TI Floppy controller DSK1. DSK2. DSK3.
Myarc & Cor Comp Floppy Controllers DSK1. DSK2. DSK3. DSK4.
Myarc HFDC DSK1. DSK2. DSK3. DSK4. WDS1. WDS2. WDS3.
Myarc HFDC with another FDC DSK5. DSK6. DSK7. DSK8. WDS1. WDS2. WDS3.
Horizon RAM disk DSK1. through DSKZ. (This depends on your configuration)
Other RAM disks DSK5. through DSK9.

 

In the documentation WHT SCSI Host Adapter

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The SCSI card provides WDS device names (and low level >2x routines) for better compatibility with programs written for the HFDC.  If alone in the system, the hfdc and scsi work comparably well. 
 

However, while true that you can use both an HFDC and SCSI card in the same system, it is not a good idea to do so.  Cards like this with the same device names and low level routines typically cause ‘conflicts’ similar to if you had two competing floppy-style devices in the system. This can be mitigated to some extent by programs and device selections but it is not foolproof. 
 

The IDE card is an example where both a new device name and new low level routines are used to minimize device conflict. Fred could just as easily taken the same path as the SCSI card for his DSR.  

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Actually, the WDS nomenclature predates the HFDC. It was the name used for hard disks by the Myarc Personality Card (a SASI controller) that could use two SASI hard disks. Initially, MDOS kept that usage as it was the only available Hard Disk controller, but eventually switched to HDS sometime after the HFDC was released (MDOS versions supporting HDS were released separately and to differentiate from the Personality Card disks at about the same time as MDOS 1.04 came out--with the initial HDS variant labeled HDOS 0.97 on its release).

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4 hours ago, Ksarul said:

Actually, the WDS nomenclature predates the HFDC. It was the name used for hard disks by the Myarc Personality Card (a SASI controller) that could use two SASI hard disks. Initially, MDOS kept that usage as it was the only available Hard Disk controller, but eventually switched to HDS sometime after the HFDC was released (MDOS versions supporting HDS were released separately and to differentiate from the Personality Card disks at about the same time as MDOS 1.04 came out--with the initial HDS variant labeled HDOS 0.97 on its release).

Came to say this but you beat me to it ;) I have a few of these cards and one complete setup with the original myarc drive/wd1000 enclosure

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